GitLab

The flow is:
1. Fetch store metadata as JSON (using URLFetcher)
2. Parse response in utility process (via SafeWebstoreResponseParser)
3. Parse manifest and get icon data using WebstoreInstallHelper
4. Show install UI
5. Whitelist extension ID for download and start download

Still missing are a way of informing the page that the inline install succeeded
or failed.

Also removes ExtensionTabHelper::GetCustomFrameNativeWindow, since it wasn't
actually overriding anything (the method was removed from
ExtensionFunctionDispatcher::Delegate by r74835).

R=asargent@chromium.org

Review URL: http://codereview.chromium.org/7741037

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@98712 0039d316-1c4b-4281-b951-d872f2087c98